In order to enhance the steering stability of a pneumatic tire, it is effective to enhance a flexural rigidity of a sidewall portion. For this purpose, a high modulus carcass cord is used to form a bone of the tire, or a bead apex rubber disposed in the bead portion and having a triangular cross section is increased in size.
Such a method is effective for enhancing the steering stability, but since a vertical rigidity of the tire is also increased, the riding comfort is deteriorated. In recent years, it has been found from various experiments that if the height of the bead apex rubber is increased to increase the vertical rigidity, road noise performance (noise inside the vehicle) is deteriorated, and especially the noise performance in a low frequency band of about 100 to 160 Hz is deteriorated.
The present inventors carried out various experiments to enhance, in excellent balance, basic performance of a tire such as steering stability, riding comfort, noise performance. As a result, they found that if intermediate elongations of carcass cords are made different in each portion of the tire, more specifically, if intermediate elongations Es at a maximum width position where a ply body portion of a carcass projects most outward in the tire axial direction are made smaller than intermediate elongation Eb at a height position of a radially outermost end of the bead core, the basic performance of the tire can be enhanced in excellent balance.
That is, it is an object of the present invention to provide a pneumatic tire capable of enhancing, in excellent balance, basic performance of a tire such as steering stability, riding comfort, noise performance.